Phlebotomus papatasi Saliva Inhibits Protein Phosphatase Activity and Nitric Oxide Production by Murine Macrophages

Department of Parasitology, The Kuvin Center for the Study of Infectious and Tropical Diseases, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Infection and Immunity (Impact Factor: 3.73). 04/1998; 66(4):1534-7.
Source: PubMed


Leishmania parasites, transmitted by phlebotomine sand flies, are obligate intracellular parasites of macrophages. The sand fly Phlebotomus papatasi is the vector of Leishmania major, a causative agent of cutaneous leishmaniasis in the Old World, and its saliva exacerbates parasite proliferation and lesion growth in experimental cutaneous leishmaniasis. Here we show that P. papatasi saliva contains a potent inhibitor of protein phosphatase 1 and protein phosphatase 2A of murine macrophages. We further demonstrate that P. papatasi saliva down regulates expression of the inducible nitric oxide synthase gene and reduces nitric oxide production in murine macrophages. Partial biochemical characterization of the protein phosphatase and nitric oxide inhibitor indicated that it is a small, ethanol-soluble molecule resistant to boiling, proteolysis, and DNase and RNase treatments. We suggest that the P. papatasi salivary protein phosphatase inhibitor interferes with the ability of activated macrophages to transmit signals to the nucleus, thereby preventing up regulation of the induced nitric oxide synthase gene and inhibiting the production of nitric oxide. Since nitric oxide is toxic to intracellular parasites, the salivary protein phosphatase inhibitor may be the mechanism by which P. papatasi saliva exacerbates cutaneous leishmaniasis.

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    • "parasites (2, 3). SGS from Phlebotomus duboscqi, a vector for Leishmania major, was chemoattractive for mouse monocytes (4) whereas SGS from Phlebotomus papatasi, another vector of L. major, inhibited macrophage activation by IFN-γ (5) and downregulated Inducible Nitric Oxide Synthase (iNOS) expression, thereby reducing NO production in murine macrophages (6). These results imply that Leishmania parasites exploit these effects to ascertain survival within infected host cells. "
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    ABSTRACT: Leishmaniases are worldwide diseases transmitted to the vertebrate host by the bite of an infected sand-fly. Sand-fly biting and parasite inoculation are accompanied by the injection of salivary molecules, whose immunomodulatory properties are actively being studied. This mini review focuses on how the interactions between sand-fly saliva and the immune system may shape the outcome of infection, given its immunomodulatory properties, in experimental models and in the endemic area. Additionally, we approach the recent contributions regarding the identification of individual salivary components and how these are currently being considered as additional components of a vaccine against leishmaniasis.
    Frontiers in Immunology 11/2013; 4:375. DOI:10.3389/fimmu.2013.00375
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    • "Co-injection of Leishmania and salivary gland homogenates from either Lutzomyia longipalpis or Phlebotomus papatasi in naïve mice produces a substantial increase in lesion size and parasite burden. The increase in infectivity was associated with the capacity of the saliva to selectively inhibit antigen presentation and nitric oxide (NO) and hydrogen peroxide production thus inhibiting the ability of macrophages to kill the intracellular parasites [5,6]. Furthermore, Leishmania vector saliva inhibits the production of protective type 1 cytokines such IL-12 and IFN-γ [7-9], while enhancing the production of interleukin (IL)-10, IL-4, IL-6 and prostaglandin E (PGE)2, all of which enhance parasite survival [10-13]. "
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    ABSTRACT: Background Leishmania parasites are transmitted to their vertebrate hosts by infected Phlebotomine sand flies during the blood meal of the flies. Sand fly saliva is known to enhance Leishmania spp. infection, while pre-exposure to saliva protects mice against parasitic infections. In this study, we investigated the initial inflammatory leucocyte composition induced by one or three inocula of salivary gland extract (SGE) from Lutzomyia longipalpis in the presence or absence of Leishmania braziliensis. Results We demonstrated that inoculating SGE once (SGE-1X) or three times (SGE-3X), which represented a co-inoculation or a pre-exposure to saliva, respectively, resulted in different cellular infiltrate profiles. Whereas SGE-1X led to the recruitment of all leucocytes subtypes including CD4+ T cells, CD4+CD25+ T cells, dendritic cells, macrophages and neutrophils, the immune cell profile in the SGE-3X group differed dramatically, as CD4+ T cells, CD4+CD25+ T cells, dendritic cells, macrophages and neutrophils were decreased and CD8+ T cells were increased. The SGE-1X group did not show differences in the ear lesion size; however, the SGE-1X group harbored a higher number of parasites. On the other hand, the SGE-3X group demonstrated a protective effect against parasitic disease, as the parasite burden was lower even in the earlier stages of the infection, a period in which the SGE-1X group presented with larger and more severe lesions. These effects were also reflected in the cytokine profiles of both groups. Whereas the SGE-1X group presented with a substantial increase in IL-10 production, the SGE-3X group showed an increase in IFN-γ production in the draining lymph nodes. Analysis of the inflammatory cell populations present within the ear lesions, the SGE-1X group showed an increase in CD4+FOXP3+ cells, whereas the CD4+FOXP3+ population was reduced in the SGE-3X group. Moreover, CD4+ T cells and CD8+ T cells producing IFN-γ were highly detected in the ears of the SGE-3X mice prior to infection. In addition, upon treatment of SGE-3X mice with anti-IFN-γ monoclonal antibody, we observed a decrease in the protective effect of SGE-3X against L. braziliensis infection. Conclusions These results indicate that different inocula of Lutzomyia longipalpis salivary gland extract can markedly modify the cellular immune response, which is reflected in the pattern of susceptibility or resistance to Leishmania braziliensis infection.
    BMC Microbiology 05/2013; 13(1):102. DOI:10.1186/1471-2180-13-102 · 2.73 Impact Factor
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    • "For example, Ixodes ricinus salivary gland extract (SGE) inhibits the killing of Borrelia afzelii by macrophages, and reduces superoxide and NO production [25]. Saliva of the sand-fly Phlebotomus papatasi contains a potent inhibitor of macrophage protein phosphatase 1 and 2A [26], and reduces inducible NO synthase (iNOS) mRNA and NO production [26]. Sand fly saliva also inhibits antigen presentation [27] and TNF-α production, while enhancing IL-6, IL-10, and intracellular cyclic-AMP accumulation in macrophages [28]. "
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    ABSTRACT: West Nile virus (WNV) is transmitted during mosquito bloodfeeding. Consequently, the first vertebrate cells to contact WNV are cells in the skin, followed by those in the draining lymph node. Macrophages and dendritic cells are critical early responders in host defense against WNV infection, not just because of their role in orchestrating the immune response, but also because of their importance as sites of early peripheral viral replication. Antigen-presenting cell (APC) signals have a profound effect on host antiviral responses and disease severity. During transmission, WNV is intimately associated with mosquito saliva. Due to the ability of mosquito saliva to affect inflammation and immune responses, and the importance of understanding early events in WNV infection, we investigated whether mosquito saliva alters APC signaling during arbovirus infection, and if alterations in cell recruitment occur when WNV infection is initiated with mosquito saliva. Accordingly, experiments were performed with cultured dendritic cells and macrophages, flow cytometry was used to characterize infiltrating cell types in the skin and lymph nodes during early infection, and real-time RT-PCR was employed to evaluate virus and cytokine levels. Our in vitro results suggest that mosquito saliva significantly decreases the expression of interferon-beta and inducible nitric oxide synthase in macrophages (by as much as 50 and 70%, respectively), whilst transiently enhancing interleukin-10 (IL-10) expression. In vivo results indicate that the predominate effect of mosquito feeding is to significantly reduce the recruitment of T cells, leading the inoculation site of mice exposed to WNV alone to have up to 2.8 fold more t cells as mice infected in the presence of mosquito saliva. These shifts in cell population are associated with significantly elevated IL-10 and WNV (up to 4.0 and 10 fold, respectively) in the skin and draining lymph nodes. These results suggest that mosquito saliva dysregulates APC antiviral signaling, and reveal a possible mechanism for the observed enhancement of WNV disease mediated by mosquito saliva via a reduction of T lymphocyte and antiviral activity at the inoculation site, an elevated abundance of susceptible cell types, and a concomitant increase in immunoregulatory activity of IL-10.
    PLoS ONE 07/2010; 5(7):e11704. DOI:10.1371/journal.pone.0011704 · 3.23 Impact Factor
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